Many semiconductor integrated circuits contain blocks that operate at different supply voltage levels. A CMOS circuit may include blocks that operate at different supply voltage levels in order to reduce power consumption. In CMOS technology, both the dynamic and the leakage power consumption depend upon the supply voltage, and they decrease quadratically with decreasing supply voltage. The supply voltage may be decreased in non-critical parts of an integrated circuit. Furthermore, the supply voltage may be regulated dynamically according to current performance requirements. As a consequence, many voltage domains may be formed on a single integrated circuit.
When a signal traverses on-chip voltage domains, a level shifter is required. The level shifter may serve as an interface between different blocks to shift a voltage level of a signal of one block to an appropriate voltage level of another block. Level shifters that are required to interface different voltage domains should be able to efficiently convert any voltage level to any other desired voltage level.